Method of manufacturing reinforced plastic foam in sheet form



Jan. 17, 1967 w w 3,298,884

METHOD OF MANUFACTURING REINFORCED PLASTIC FOAM IN \SHEVET FORM OriginalFiled April 25, 1961 4 Sheets-Sheet 1 INVENTOR 8 h W E, 137 74 113%,

ATTORNEYS J. WILLY METHOD OF MANUFACTURING REINFORCED Jan. 17, 1967 EETFORM Original Filed April 26,

PLASTIC FOAM IN SH 1961 v 4 Sheets-Sheet 2 INVENTOR John Willy BY J.WILLY METHOD OF MANUFACTURING REINFORCED PLASTIC FOAM IN SHEET FORM 1961Original Filed April 25 4 Sheets-Sheet 5 INVENTOR Jan. 17, 1967 J. WILLY3,298,884

METHOD OF MANUFACTURING REINFORCED I PLASTIC FOAM IN SHEET FORM OriginalFiled April 25, 1 s1 4 Sheets-Sheet 4 FIG. 9

I INVENTCSR. K fNQHN w| -LY BY 4M 1 J- ATTORNEYS United States Patent3,325,834 METHOD 0F MANUFACTURING REINFORCED PLASTIC FOAM IN SHEET FORMJohn Willy, Attleboro, Mass, assignor to Specialty Converters, Inc., acorporation of Delaware Filed Get. 7, 1965, Ser. No. 493,641 3 Claims.(Cl. 156-79) tensile strength renders them unsuitable for many useswhere otherwise they could be of great advantage. This is especiallytrue of flexible or semirigid foams, but applies oftentimes to rigidfoams as well. A distinct need exists, therefore, for a plastic foammaterial, particularly in economical sheet form, which has all theadvantages of ordinary foam but is capable of bearing tensile loads inone or more directions without tearing or perhaps without evenstretching. The broad purpose of this invention is to provide reinforcedplastic foam sheet which achieves these ends.

Typical known designs of reinforced plastic foam sheets are of laminatedor composite construction wherein separate foam sheets are adheredtogether witha reinforcing material between them. Such sheets areconsiderably more costly than ordinary foam, of course, because thelaminating process is entirely separate from the manufacture of the twoor more individual component sheets. Also, the presence of an adhesivein the composite product sometimes renders the product less resilientand flexible, more dense, less absorbent, etc. than ordinary homogeneousfoam. Consequently, the reinforced foam sheets available heretofore havebeen relatively expensive specialty products which are far lessversatile than plain foam sheets.

The foamed plastic product made by the method and with the apparatus ofthis invention comprises a unitary sheet of plastic foam of greatbreadth and length relative to its thickness. The sheet has a unitaryand continuous cellular structure throughtout with a relativelycoarse-pore internal structure throughout its thickness exceptimmediately adjacent its broad surface faces and having at such faces askin of relatively fine-pore structure integral with said internalstructure and forming a substantially smooth continuous even integralsurface film resistant to penetration of surface coatings appliedthereto. A flexible discontinuous reinforcing layer comprising spacedfilamentary reinforcing elements is disposed within said sheet betweenand substantially parallel to the broad faces thereof. The body of thesheet is foamed in situ integrally through the interstices between thereinforcing elements and possesses substantially the same pore structurewithin such interstices as on opposite sides of the reinforcingelements. The discontinuous layer of reinforcing material may be of manyforms, perhaps an open mesh screen or a number of parallel strands laidside-by-side, or a mat of at least one randomly looped strand. Thesestrands may bend easily so as to render the sheet practically asflexible as any unreinforced foam, or they may be self-supporting so"ice that the new reinforced foam can be for-med into and hold anyshape. Furthermore, the strands may be of metal, or they may benon-metallic and perhaps stretchable longitudinally to a certain extentif desired. The reinforcing layer may also comprise .at least oneelectrically conductive wire laid without crossing in contact withitself, so that with electrical connecting means at the opposite ends ofthe wire such a sheet may provide an electrical heating pad. Also, thenew foamed plastic sheet has an integral skin layer on both of its broadfaces, and this skin has a substantially finer exterior pore structurethan the interior pore structure within the sheet.

It is important to note that, whatever the form of the discontinuouslayer of reinforcing material may be, the cellular structure of the foamis entirely unitary and extends integrally through the reinforcing layerand around the strands thereof. Consequently, the new product is asingle sheet possessing substantially all the advantages of ordinaryfoam, from the standpoint both of cost and physical properties, exceptthat it will not tear when subjected to tension or shear forces in oneor more directions.

The method is in combination with one of making a unitary single sheetof flexible polyurethane foam which has a unitary and continuouscellular structure throughout wherein a liquid polyurethane foamingmixture is continuously prepared and chilled below room temperature to atemperature at which it will not react to delay foaming thereof. Thechilled mixture is spread onto a moving flexible carrier web and amoving flexible covering web is directed over the foam mixture toposition the mixture between the carrier and covering webs. A uniformthickness of chilled foam mixture is fixed between the carrier andcovering webs; the temperature of the foam mixture is raised to reactthe mixture and form a foam sheet between the webs; the webs with thefoam therebetween are directed into a preliminary heat curing zone; thecarrier and covering webs are separated from the foam sheet, and thefoam sheet is directed to a final curing operation. The improvement isin reinforcing the foam sheet with a flexible discontinuous reinforcinglayer embedded within the foam sheet and extending substantiallyparallel to the broad faces thereof. It comprises the steps of feeding adiscontinuous layer of spaced reinforcing strands into the chilledfoaming mixture, controlling the angle of entry of said reinforcingmaterial into said chilled foam mixture in relation to its positionbetween the broad faces of the sheet to deter-mine its final positionbetween the broad faces of the sheet, compressing the carrier and coversheets toward each other to squeeze excess mixture from between thewebs'and force the remainder of themixture fully through and around thestrands of said reinforcing layer before foaming of the mixture to fillthe interstices and coat the strands with said foaming mixture andthereby entirely enclose the reinforcing layer in the foaming mixture,thereafter freeing the webs from the squeezing action to allow themixture therebetween to foam, moving the webs reinforcing layer and foammix-ture together at a constant rate, and foaming the mixture in situinto a unitary foamed sheet integrally about and penetrating theinterstices between the reinforcing strands so that it possessessubstantially the same pore structure within such interstices as on theopposite sides of the reinforcing elements.

Preferably, the flexible carrier and covering webs may be directed intorolls to be pressed together, as described. Also, the angle of entry ofthe reinforcing material into the rolls may be varied in order tocontrol the location of the reinforcing material between the broad facesof the finished sheets. The pressure of the rolls on the webs esters, orpolyethers) is may be controlled too in order to determine the amount ofmixture remaining between the webs, which in turn determines thethickness of the finished sheets.

The apparatus used for making the sheets of reinforced foamed plastic isof the type which has a pair of flexible webs movable together one overthe other and defines opposed forming surfaces releasable with respectto said foamed plastic feeding means for disposing a layer of liqquidfoaming mixture between said surfaces and means permitting substantiallyfree separation of the webs after rolling so that the remaining mixturefoams therebetween about said reinforcing material, and displacementmeans for removing the web from the finished foam. The improvement is incombination with this apparatus and comprises means for feeding adiscontinuous layer of reinforcing material between the surfaces andinto the chilled mixture and apair of rolls having a resilient surfacefor forcing the webs together to squeeze the excess mixture from betweenthe forming surfaces and force the remaining mixture fully through andaround the strands of the reinforcing material before foaming of themixture to fill the interstices and coat the strands with said foamingmixture and thereby entirely enclose the reinforcing layer in thefoaming mixture.

A preferred embodiment of the invention is described hereinbelow withreference to the accompanying drawings, wherein v FIG. 1 is a schematicelevation of the new apparatus;

FIG. 2 is an enlarged fragmentary section of the carrier and coveringwebs, reinforcing material and liquid foaming mixture entering therolls;

FIG. 3 is a section enlarged over FIG. 2 and showing the compressedelements between the rolls;

FIG. 4 is a perspective view partly broken away of one embodiment of thenew reinforced foam sheet;

FIG. 5 is an enlarged section taken along the line 5-5 in FIG. 4;

FIG. 6 is a perspective view partly broken away of I another embodimentof the new product;

produced is polyurethane foam which is formed from a polyisocyanate(especially toluene diisocyanate) and a hydroxyl-containing compound (e.g; glycols, polyols, poly- The particular composition of a givenpolyurethane foam varies widely depending upon the properties desired,such as density, tensile strength, tear strength, flexibility, cellsize, and so on. For purposes of example, one specific flexible foam isdescribed herein, though it is to be understood that the inventionincludes many other flexible foams within its scope, and also semirigidor rigid foams.

It is intended that any of the foaming mixtures of the I type describedin U.S. Patent 2,956,310 can be used in this invention. In a firstexample 95 grams of an 80-20 mixture of the 2, 4, and 2, 6 isomers oftoluene diisocyanate were placed in a reaction vessel. To the toluenediisocyan ate there were added 450 grams of polypropylene glycol, havingan average molecular weight of 2000. The materials reacted with theevolution of heat, :and mixing was continued until a temperature peakwas reached, and then dropped back to about 9 F., at which time themixture was heated with stirring to a temperature of 284 F. The mixturewas then cooled to 122 F. Further toluene diisocyanate, to the extent of82 grams was added with stirring to bring the free NCO group content upto about 10%.. To the resulting prepolymer mixture, 3 grams of i a fluidsilicone oil of 50centistokes at 77F. viscosity was added and mixed in.The resultant batch weight was about 627 grams.

A catalyst mixture was then prepared by mixing into 23 grams of colddistilled water 5.0 grams of triethylene diamine and 10.0 grams ofN,N,N,N tetramethyl 1,3 butanediamine.

The prepolymer mixture was cooled to a temperature of 2 0 F. in aseparate reservoir as will be described and to grams of the coldprepolymer was added 3.85 grams of the catalyst mixture and the two wererapidly, but thoroughly intermixed for dispensing from, for example, amixing head, as below.

In a second example, a pre-mixed resin is used comprising two componentpolyether-based prepolymer systems, tag. a prepolymer of toluenediisocyanate and an organic compound having two or more diisocyanatereactive groups, with an excess of toluene diisocyanate. (Such a resinis commercially :available under the tradenarne Isofoam L-128manufactured by Isocyanate Products, Inc. of Wilmington, Delaware.) To100 parts by weight of this pre-mixed resin is added 0.5 part by weightof silicone oil, and this prepolymer mixture is placed in a reservoir 11associated with a pump 12 in the apparatus shown in FIG. 1. A catalystmixture is then prepared and placed into a reservoir 13 associated witha pump 14; this catalyst mixture comprises 0.5 part by weight oftriethylene diamine dissolved in 1.3 parts by weight of N,N,N,tetramethylbutane diamine and 2.0 parts by weight'of distilled water.Under certain circumstances, Freon may replace the water content.

The pumps 12 and 14 deliver their respective reactants continuously to aconventional mixing head 16 at accurate- 1y determined rates. The speedof the pump 12 is adjusted to give a discharge rate of just slightlyless than the total discharge of liquid foaming mixture desired from thefoaming head 16, and the speed of the catalyst 14 is then adjustedaccordingly to give a discharge rate of 3.8 percent of that establishedin the pump 12.

The preparation of the foam-forming reactants in this manner is withinthe knowledge of the art and is not itself a part of this invention.Thus, the prepolymer components may be separately stored and pumpedrather than pie-mixed as described above, in which case a thirdreservoir and pump would be provided. Pigments may also be added asdesired to color the foamed sheet product, but it should be noted thatthey must either be dehydrated or of closely controlled moisture contentin order to not unbalance. the crucial water content of the mixture.

Suitable cooling coils are included in each of the tanks 11 and 13 andalso in association with the mixing head to insure that the mixture ischilled below room temperature to further delay foaming. Advantageously,each of the primary ingredients is chilled to 20 F. in the tank, andthey should be no warmer than 50- F. after being dispensed from the head16.

The mixing head 16 is supported by a suitable traversing mechanism,including for example rollers 18 and tracks 19, enabling it to beoscillated slowly back and forth in a direction perpendicular to theplane of the drawing in FIG. 1. As the head 16 indexes back and forth,the liquid polyurethane foaming mixture described above flows from itsnozzle through a curved guide tube 20 and onto the upper or carriersurface of a carrier web 21 which moves over a table 22in a direction atright angles to the traversing motion of the head 16. The upper surfaceof the carrier web 21 is coated with a release agent (such as siliconerubber, polyethylene, wax or polytetrafluoroethylene) and theweb bodybehind this release agent may be woven fabric, thin sheet metal, or anyother suitable flexible sheet. As shown in FIG. 1, the carrier web 21 isendless and passes over a series of supporting rolls 23, at least someof which are also driving rolls which advance the web 21 in thedirection of the arrow at. a uniform rate.

In FIG. 2, a stream of the foaming mixture is shown flowing downwardlyfrom the head 16 onto the carrier web 21 which moves over the table 22.The head 16 is traversed back and forth at a sufficient rate (say .360degrees per minute) so that a sufiiciently thick layer of the foamingmixture isapplied to the carrier web 21. After leaving the table 22, thecarrier web 21 enters a pair of opposed doctoring rolls 28 and 29 whichare advantageously coated with layers 30 and 31 respectively of rubberor other resilient material. As shown in FIG; 1, the upper roll 28 ismounted on an adjustable support 33 which permits the distance betweenits axis and the axis of the lower roll 29 to be varied as desired. Thisallows adjustments ranging from a wide gap between the rolls to tightcontact between their resilient surfaces.

As the carrier web 21 is drawn between the rolls 28 and 29, it comes inopposition with the underside of a covering web 35 whichis directedaround the upper roll 28. The covering web 35 is also an endless belt,and like the carrier web 21 may be coated with a release agent. It toois supported and driven by' a plurality of rolls 36. This constructionpermits the carrier web 21 to be moved together with the covering web 35in direct surface-to.- surface opposition relative thereto.

Advantageously, the release agent and backing material of the webs 21and 35 are resilient and compressible so that the webs canbe squeezedtogether and advanced through the rolls 28 and 29 even when the roll gapis zero, i.e. surface-to-surface contact. However, depending upon thethickness of the desired foamed sheet, the roll 28 may be raised orlowered by means of the adjustable support 33 to vary the roll gap andincrease or decrease the thickness of the resulting sheet. Very littlemixture is necessary between the webs to produce a sheet of substantialthickness; for example, a roll gap of only .020 inch will produce asheet /2 inch thick when the foaming mixture described previously isused. As shown in FIG. 2, a bead 38 of excess foaming mixture iscontinuously squeezed forward in front of the rolls 28 and 29 so thatjust the desired amount of mixture remains between the webs .to foaminto a sheet of the predetermined thickness.

Also directed between the rolls 28 and 29 is a discontinuous layer ofreinforcing material 39 which is fed from a supply roll 40. Thisreinforcing material may vary widely as is described hereinbelow, butfor purposes of this example it may be said to be an open mesh screen ofsaran strands. (Saran is a thermoplastic resin obtained by thepolymerization of vinylidene chloride or copolymerization of vinylidenechloride with lesser amounts of other unsaturated compounds.) The screenis drawn'between the rolls 28 and 29 by the webs 21 and 35, and underthe pressure of the rolls the remaining liquid foaming mixture betweenthe webs is forced fully through the open mesh of the screen and aroundthe individual strands thereof. This entirely encloses the reinforcingmaterial in the foaming mixture. t t

In FIG. 3, the element-s between the rolls are shown in typical tightcompression. It will be noted that under such heavy roll pressure thewebs 21 and 35 are squeezed to the point where their adjacent surfacesactually conform somewhat to the irregular surface of the reinforcingmaterial 39, leaving very little of the foaming mixture therebetween andinsuring that the small remaining amount is forced fully aroundthestrands of the reinforcing material 39.

In one example, the rolls were set to provide a clearance of 0.004 inchbetween the carrier web 21 and the covering web 35 at the nip of therolls with a reinforcing material having a thickness of 0.007. There wasa negative noll' gap and the reinforcing material could pass through themetering section only because of the resiliency of the rolls and thecompressibility of the reinforcing sheet. Using the first example of thefoam mixture described a foam sheet having a thickness of ,1 inch wasformed.

In another example, also using the first example of foam mixturedescribed with a reinforcing material having a thickness of 0.007 aclearance of 0.004 more than the thickness of the reinforcing materialwas maintained between the carrier web 21 and the covering web 35 andthe foam sheet formed had a thickness of inch.

It has been found that the final position of the reinforcing layerbetween the broad faces of the finished strip may be controlled byadjusting the angle of entry of the reinforcing material into the rolls28 and 29. In other words, if the reinforcing material 39 enters therolls at the angle shown in FIG. 2 relative to the carrier web 21, itwill have a certain location between the broad faces of the finishedfoamed sheet. If this angle is increased such that the reinforcingmaterial 39 is initially directed closer to the covering web 35 and moreremote from the carrier web 21, then the reinforcing material will becloser to the upper broad face of the finished foam sheet. The converse,of course, is equally true. Apparently, this happens because more orless of the foaming mixture is situated on one or the other side of thereinforcing material 39 between the rolls 28 and 29 depending upon theinitial angle of entry of the reinforcing material into the rolls. Inorder to make these adjustments, the supply roll 40 of'the reinforcingmaterial 39 may be raised or lowered as desired by the adjustment means41 shown in FIG; 1. At the angle shown in FIG. 2, the reinforcingmaterial was wetted by the foaming mixture equally at both the top andbottom, and this resulted in a product in which the reinforcing layerwas substantially in the center of the foam and substantially parallelto the broad faces. Referring to FIG. 9, the supply roll 40 has beenraised to increase the angle of entry relative to the horizontal carrierbelt; Here the reinforcing material 39 came into light contact with thecovering web with the major rolling bank of foaming mixture below thepart of level of the reinforcing material. With this adjustment, thefoaming mixture was disposed substantially as the lower side of thereinforcing material; thus, the foam sheet formed had the reinforcinglayer located near and parallel to the surface face of the foam sheet.Therefore, by regulation of the angle of entry of the reinforcingmaterial into the nip of the roller in conjunction with the control ofits tension against the cover sheet, the position of the reinforcinglayer could be varied from adjacent the broad surface of the sheet tovarious depths into the center.

Shortly after leaving the rolls 28 and 29, the foaming mixture beginstoexpand and form a foam structure as shown at 43 in FIG. 2. The webs 21and 35 are free to move apart at this time so that the foaming takesplace with relatively little resistance. It is characteristic of theinvention that as the mixture starts to foam, the cellular structure isgenerated in situ about the open mesh of the reinforcing screen on bothsides thereof so that a completely unitary foam sheet is created aroundthe reinforcement.

Moving together at a constant rate, for example 20 feet per minute, thewebs 21 and 35 then carry the newlyformed foam into a preliminaryheat-curing stage of three separate heating zones. These comprise threecovers 45, 46, and 47 extending perhaps half a foot above the webs andenclosing steam heating coils 48, 49, and 50 respectively which elevatethe temperature therein to three successively higher levels. With theparticular foam sheet product described herein, these covers may each beabout 20 feet long and maintain temperatures of F., F., and 245 F.respectively. Taken with the 20 foot per minute advance of the webs 21and 35, these temperatures and distances leave the polyurethane foam ina semi-cured but self-supporting condition upon emerging from the end ofthe last cover 47.

At that exit point, the endless webs 21 and 35 leave the partly curedreinforced foam sheet (indicated at 52 'in FIG." 1), and the sheetpasses over an idler roll 53 and moves into a final heat-curing oven 54.During the final heat-curing the reinforced foamed sheet 52 advancesover a series of festoon rolls 55 until it is fully cured. Upon emergingfrom the final heat-curing oven 54 the finished sheet is wrapped upabout an'end product roll 56.

Referring now to FIGS. 4-8, enlarged views of various embodiments ofreinforced foam according to the invention are shown. In each of them,the flat broad faces of the sheet have a distinctive skin-like surfaceof con si-derably finer exterior pore structure than the interior foamedstructure within the sheet. This is because the cellular structure atthese broad faces is generated while in contact with the carrier andcovering webs 21 and 35 respectively and thus cannot foam to the fullporosity achieved elsewhere in the sheet. This gives a very pleasingappearance and a good feel to the sheet product and provides a surfacesomewhat more resistant to tearing.

In FIG. 4, the product comprises a unitary polyrethane sheet 58 foamedintegrally about an open mesh 59. Again, this mesh 59 may be of variousstrand material, such as the saran fibers described previously,monofilaments of fiber glass or nylon or any other suitable plasticmaterial, metal wire, natural fibers of cotton or jute or the like, orvarious other yarn-s whether twisted or stranded, etc. Its weave may beperpendicular or on the bias with respect to the longitudinal axis ofthe indefinite length sheet made according to the method and apparatusof FIGS. 1 and 2. The primary characteristic of this reinforcing layerand all the others described herein is that it is discontinuous so thatthe foam structure may form completely and integrally there through andaround the strands thereof. Thus, the open mesh 59 may be a plurality ofunwoven crisscrossed wires Whether adhered together or not, or aflexible length of perforated sheet material, or any other reinforcingsheet-like article having interstices through which. the foam cangenerate.

FIG. 5 is an enlarged edge view of the FIG. 4 product; it shows thereinforcing screen 59 spaced about midway between the broad faces of thesheet, though it could be closer to one or the other of them dependingupon its initial angle of entry into the rolls. This section also showsthe unitary cellular structure extending fully through the reinforcinglayer and around the strands thereof.

FIG. 6 shows an embodiment of the product wherein a plurality ofparallel wires 61 make up the reinforcing layer. These wires are laidside-'by-side and may be directed from an array of spools positionedmuch like the supply roll 40 and fed into the rolls 28 and 29. It ischaracteristic of the FIG. 6 product that it resists stretching whenpulled longitudinally because of the strands 61, but when pulledlaterally with respect to the strands it stretches easily. direction ofthe strands, some stretching may be provided, as with saran fibers whichmay stretch up to 18 percent before failing.

Turning now to the embodiment of FIG. 7, the unitary polyurethane foamedsheet there includes a layer of reinforcing material made up of one ormore randomly looped strands 62 disposed in a mat. Again, the particularfilament used for this mat can vary. This reinforcing layer does notwithstand tension during its manufacture, of course, and thus must belaid directly on the carrier web 21 rather than pulled tightly betweenthe webs by the rolls 28 and 29. In general, the purpose of the randomlylooped filament in FIG. 7 is to increase resistance to tearing.

In FIG. 8, another embodiment of the new reinforced polyurethane foamedsheet is shown in which the reinforcing srand is an electricallyconductive wire 63 laid in continuous loops without crossing in contactwith itself. At the desired point along the length of such strip,

Even in the longitudinal 8 the ends of wire may be brought out andformed with suitable electrical terminals 64 and 65.

The embodiment of FIG. 8 constitutes a type of electrically heatedelement which may be used as a heating pad, blanket, wrapping or thelike. The wire 63 may be laid back and forth as shown by anyconventional traversing feed mechanism, or it may be disposed in anyother suitable arrangement. If laid back and forth as shown, more thanone such Wire may be so disposed in respective longitudinal zones of thesheet so that several strips of the product may be taken from a givensheet. Alternatively, a plurality of wires may be laid side-byside' asin the FIG. 6 embodiment, and thereafter the extended sheet may be cutto length and the exposed ends of adjacent pairs of the wires may beelectrically bridged to permit'current to pass from one wire to theother through the sheet. Actually, any pattern of electricallyconductive wires embedded within the unitary foam sheet is suitable forthe heating pad herein contemplated, so longas a continuous circuit isestablished within the sheet. If desired, such heating pads may befurther strengthened by the addition of any one of the previouslydescribed non-metallic reinforcing layers.

I claim:

1. In a method of making a unitary single sheet of flexible polyurethanefoam having a unitary and continuous cellular structure throughoutwherein a liquid polyurethane foaming mixture is continuously preparedand chilled below room temperature to a temperature at which it will notreact to delay foaming thereof, spreading the chilled mixture onto amoving flexible carrier web, directing a moving flexible covering webover the foam mixture to position the mixture between the carrier andcovering webs, fixing a uniform thickness of the chilled foam mixturebetween the carrier and covering webs, raising the temperature of thefoam mixture to react the mixture and form a foam sheet between thewebs, directing the webs with the foam therebetween into a preliminaryheat-curing zone, separating the carrier and covering webs from the foamsheet, and directing the foam sheet t'o'a final curing operation, theimprovement in-combination therewith of reinforcing the foam sheet witha flexible discontinuous reinforcing layer embedded within said foamsheet and extending substantially parallel to the broad faces thereofcomprising:

(a) feeding a discontinuous layer of spaced reinforcing strands into theliquid foaming mixture at a first position where it is still chilled andbefore any foaming has occurred,

(b) controlling the angle of entry of said reinforcing material intosaid chilled foam mixture at said first position in relation to itsposition between the broad faces of the sheet to determine its finallocation between the broad faces of the sheet so that decreasing theangle relative to one of the broad faces at the first position finallypositions the reinforcing angle closer to that face,

(c) compressing the carrier and cover webs toward each other at thefirst position to squeeze excess mixture from between the webs and forcethe remainder of said mixture fully through and around the strands ofsaid reinforcing layer before foaming of the mixture to fill theinterstices and coat the strands with said foaming mixture and therebyentirely enclose the reinforcing layer in the foaming mixture,

((1) freeing the webs from said squeezing action at a second position toallow the mixture therebetween to foam,

(e) moving the webs, reinforcing layer and foam mixture together at aconstant rate, and

(f) foaming said mixture in situ into a unitary foamed sheet integrallyabout and penetrating the interstices between the reinforcing strands sothat it possesses substantially the same pore structure within suchinterstices as on the opposite sides of the reinforcing elements.

2. A method according to claim 1 wherein said first position is definedby a nip between a pair of opposed resilient rolls and compression ofwebs .is effected at the nip of the rolls.

3. A method according to claim 2 wherein the size of References Cited bythe Examiner UNITED STATES PATENTS Alderfer 156-78 X Runton 156-78 XRoop et a1. 156-79 X House 161-89 X Coble 156-79 Mathues et a1. 156-79 Xthe nip is varied depending upon the thickness of the 10 EARL BERGERTPrimary CLIFTON B. COSBY, Examiner.

sheet to be formed.

1. IN A METHOD OF MAKING A UNITARY SINGLE SHEET OF FLEXIBLE POLYURETHANEFOAM HAVING A UNITARY AND CONTINUOUS CELLULAR STRUCTURE THROUGHOUTWHEREIN A LIQUID POLYURETHANE FOAMING MIXTURE IS CONTINUOUSLY PREPAREDAND CHILLED BELOW ROOM TEMPERATURE TO A TEMPERATURE AT WHICH IT WILL NOTREACT TO DELAY FOAMING THEREOF, SPREADING THE CHILLED MIXTURE ONTO AMOVING FLEXIBLE CARRIER WEB, DIRECTING A MOVING FLEXIBLE COVERING WEBOVER THE FOAM MIXTURE TO POSITION THE MIXTURE BETWEEN THE CARRIER ANDCOVERING WEBS, FIXING A UNIFORM THICKNESS OF THE CHILLED FOAM MIXTUREBETWEEN THE CARRIER AND COVERING WEBS, RAISING THE TEMPERATURE OF THEFOAM MIXTURE TO REACT THE MIXTURE AND FORM A FOAM SHEET BETWEEN THEWEBS, DIRECTING THE WEBS WITH THE FOAM THEREBETWEEN INTO A PRELIMINARYHEAT-CURING ZONE, SEPARATING THE CARRIER AND COVERING WEBS FROM THE FOAMSHEET; AND DIRECTING THE FOAM SHEET TO A FINAL CURING OPERATION, THEIMPROVEMENT IN COMBINATION THEREWITH OF REINFORCING THE FOAM SHEET WITHA FLEXIBLE DISCONTINUOUS REINFORCING LAYER EMBEDDED WITHIN SAID FOAMSHEET AND EXTENDING SUBSTANTIALLY PARALLEL TO THE BROAD FACES THEREOFCOMPRISING: (A) FEEDING A DISCONTINUOUS LAYER OF SPACED REINFORCINGSTRANDS INTO THE LIQUID FOAMING MIXTURE AT A FIRST POSITION WHERE IT ISSTILL CHILLED AND BEFORE ANY FOAMING HAS OCCURRED, (B) CONTROLLING THEANGLE OF ENTRY OF SAID REINFORCING MATERIAL INTO SAID CHILLED FOAMMIXTURE AT SAID FIRST POSITION IN RELATION TO ITS POSITION BETWEEN THEBROAD FACES OF THE SHEET TO DETERMINE ITS FINAL LOCATION BETWEEN THEBROAD FACES OF THE SHEET SO THAT DECREASING THE ANGLE RELATIVE TO ONE OFTHE BROAD FACES AT THE FIRST POSITION FINALLY POSITIONS THE REINFORCINGANGLE CLOSER TO THAT FACE, (C) COMPRESSING THE CARRIER AND COVER WEBSTOWARD EACH OTHER AT THE FIRST POSITION TO SQUEEZE EXCESS MIXTURE FROMBETWEEN THE WEBS AND FORCE THE REMAINDER OF SAID MIXTURE FULLY THROUGHAND AROUND THE STRANDS OF SAID REINFORCING LAYER BEFORE FOAMING OF THEMIXTURE TO FILL THE INTERSTICES AND COAT THE STRANDS WITH SAID FOAMINGMIXTURE AND THEREBY ENTIRELY ENCLOSE THE REINFORCING LAYER IN THEFOAMING MIXTURE, (D) FREEING THE WEBS FROM SAID SQUEEZING ACTION AT ASECOND POSITION TO ALLOW THE MIXTURE THEREBETWEEN TO FOAM, (E) MOVINGTHE WEBS, REINFORCING LAYER AND FOAM MIXTURE TOGETHER AT A CONSTANTRATE, AND (F) FOAMING SAID MIXTURE IN SITU INTO A UNITARY FOAMED SHEETINTEGRALLY ABOUT AND PENETRATING THE INTERSTICES BETWEEN THE REINFORCINGSTRANDS SO THAT IS POSSESSES SUBSTANTIALLY THE SAME PORE STRUCTUREWITHIN SUCH INTERSTICES AS ON THE OPPOSITE SIDES OF THE REINFORCINGELEMENTS.